Insurgents detonated twin car bombs near Iraq's Interior Ministry in Baghdad Thursday, killing at least 15 people and injuring dozens of others. Insurgents have carried out a series of attacks this week on Iraqi police and security forces.

Witnesses say two bombers triggered the explosives as a police convoy passed near the Interior Ministry. Policeman Waleed Hadi says no one in the convoy was killed, but the attack ripped through nearby cars along a crowded street.

He says the two bombers apparently targeted the passing convoy. One device was detonated at the rear of the convoy and the second at the front.

After the blasts, American forces safely detonated a third car bomb found in the area.

The al-Qaida terrorist network in Iraq claimed responsibility for the attack, but the claim, made on an Islamist Web site, was impossible to verify.

Also in Baghdad, unknown attackers shot and killed Lieutenant Firas Hamid on his way to work at Iraq's intelligence service.

In the northern city of Kirkuk, insurgents opened fire with machine guns and mortars, killing four policemen and injuring three others. Wednesday, nine officers were killed in a blast in the city, while trying to defuse a bomb.

Gunmen also killed an officer on patrol in the central Iraqi city of Baqubah.

In Washington, the White House says it remains in touch with the family of a U.S. civilian seized from a water treatment plant near Baghdad this week. The Al-Jazeera television network showed a videotape Wednesday of the man, Jeffrey Ake, being held by an unidentified militant group.

Mr. Ake is the owner of a U.S.-based company that makes water bottling machinery, and had been working to install bottling facilities in Baghdad.

He is the first American to appear in a hostage video since last fall, when insurgents abducted and killed two Americans in Iraq.

Currently, militants are also believed to be holding three Romanian journalists.